The invention relates to a calculating device provided with scales for calculating radioactive doses and intensities. By dose is understood the sum of the separate products of intensity and duration of exposure.
A calculating device of this kind is known from an article by B. W. Soole, entitled "The RADIAC slide rule for the computation of external radiation dose from nuclear fission products", Journal of Scientific Instruments, June 29, 1952, pp. 189 - 192.
The known calculating device is based on the following concept. After a nuclear explosion which has released radioactive materials, radioactive radiation decreases with time. This decrease can be approximated by the formula I.sub.t = I.sub.1 .multidot.t.sup.-x, where
I.sub.t is the intensity a period of time t after the explosion,
I.sub.1 the intensity one hour after the explosion,
T THE TIME ELAPSED AFTER THE EXPLOSION AND
X A DECAY EXPONENT, FOR WHICH 1.2 IS A PRACTICAL VALUE.
Hitherto all calculating devices of this kind have been based on the aforementioned value of x = 1.2. The actual value of x, however, is influenced by the conditions under which the explosion takes place and also by the properties and the composition of the source of explosion; therefore it will generally deviate from the value 1.2. If the approximation formula given above is used, an insight is required into the variations that may arise from an exponent x differing from the average value 1.2. The magnitude of the deviation can be determined by computation for different values of x. To achieve a good approximation, a simpler working method, and a greater accuracy in calculating a different approximation formula should be used in which a deviation from the value 1.2 for the decay exponent has not such a preponderant influence.